This paper presents a set of architectures for the composition of ubiquitous computing applications. It describes research that is being carried out in "extrovert-Gadgets", a research project funded in the context of EU IST/FET proactive initiative "Disappearing Computer". This project aims to provide a conceptual and technological framework that will engage and assist ordinary people in (re)configuring or using systems composed of computationally enabled everyday objects, which are able to communicate using wireless networks (these objects are sometimes called "artifacts"). In that sense, artifacts are treated as reusable "components" of a changing everyday environment. The main idea behind the "ubiquitous computing", or "ambient computing", or "disappearing computer" concept is that the computer "disappears" and computing services are made available to users throughout their physical environment. The pro...